Methods of inspecting integrated circuit substrates using electron beams

Methods of inspecting integrated circuit substrates include the steps of directing a beam of electrons into a first conductive plug located within a first contact hole on an integrated circuit substrate and then measuring a quantity of electrons emitted from the first conductive plug to determine an absence or presence of an electrically insulating residue in the first contact hole. The quantity of electrons emitted from the first conductive plug by secondary electron emission can be measured in order to determine whether electrons are being accumulated within the conductive plug because an insulating residue is blocking passage of the electrons into an underlying conductive portion of the substrate. If an electrically insulating residue is present, then sufficient repulsive forces between the accumulated electrons will result in the secondary emission of excess electrons from an upper surface of the conductive plug as the conductive plug is being irradiated with the electron beam. A detector can then be used to measure the quantity of the emitted electrons against a threshold level, in order determine whether the quantity of electrons emitted by secondary emission is sufficient to indicate that an insulating residue is present in the contact hole.